1. Field
Example embodiments relate to apparatuses and/or methods that may program data in memory devices. Also, example embodiments relate to apparatuses and/or methods that may program data in multi-level cell (MLC) memory devices or multi-bit cell (MBC) memory devices.
2. Description of Related Art
A single-level cell (SLC) memory device may store one bit of data in a single memory cell. The SLC memory is referred to as a single-bit cell (SBC) memory. A process of storing the data in a memory cell (a single-level cell) of the SLC memory is referred to as a program process, and may change a threshold voltage of the memory cell. For example, when data of a logic value of “1” is stored in the single-level cell, the single-level cell may have a threshold voltage of 1.0 V, and when data of a logic value of “0” is stored in the single-level cell, the single-level cell may have a threshold voltage of 3.0 V.
The threshold voltage generated in each single-level cell where the same data is programmed may have a distribution within a predetermined range due to a minute electrical characteristic difference between single-level cells. For example, when a voltage read from the memory cell is higher than or equal to 0.5 V and is lower than 1.5 V, it may be determined that the data stored in the memory cell has a logic value of “1”. When the voltage read from the memory cell is higher than or equal to 2.5 V and is lower than 3.5 V, it may be determined that the data stored in the memory cell has a logic value of “0”. The data stored in the memory cell may be classified depending on the difference between currents/voltages of the memory cell during the reading operations.
Meanwhile, a multi-level cell (MLC) memory device that can store data of two or more bits in a single memory cell has been proposed in response to a need for higher integration of memory. The MLC memory device is also referred to as a multi-bit cell (MBC) memory. However, as the number of bits programmed in the single memory cell increases, reliability may deteriorate and a read-failure rate may increase. To program ‘m’ bits in the single memory cell, any one of 2m threshold voltages may need to be generated in the memory cell. Threshold voltages of memory cells where the same data is programmed may generate a distribution within a predetermined range due to the minute electrical characteristic difference between the memory cells. Each threshold voltage distribution may correspond to each of 2m data values generated by ‘m’ bits.
However, since a voltage window for a memory device may be limited, a distance between 2m distributions of threshold voltages between adjacent bits may decrease as ‘m’ increases, and the distributions may be overlapped as the distance between the distributions decreases. When the distributions are overlapped, the read-failure rate may increase.